Thermoplastic resins generally have lower specific gravity than glass or metal and also can have excellent physical properties such as compactability, impact resistance, and the like. Recently, plastic resins are rapidly replacing glass or metal in electronic goods to provide larger, more lightweight and less expensive products. Further, applications for plastic resins are expanding from electronic components to automobile parts. Accordingly, the function and appearance of plastic resins used in the production of exterior materials for various products are becoming increasingly important and demand for improved external appearance and workability of such resins is also increasing.
Acrylonitrile-butadiene-styrene copolymer (ABS) resins are prepared by dispersing a graft ABS copolymer (g-ABS) resin into a matrix polymer of a styrene-acrylonitrile copolymer (SAN) resin. The graft ABS copolymer (g-ABS) is a copolymer in which aromatic vinyl compounds (such as styrene monomers) and unsaturated nitrile-based compounds (such as acrylonitrile monomers) are grafted to a butadiene-based rubber polymer as a central or a core portion. Such ABS resins have excellent properties, such as workability, impact resistance, heat resistance, chemical resistance, mechanical strength, melt strength and the like, and also have excellent coloring properties and gloss. Accordingly, ABS resins are widely used in various electric, electronic and miscellaneous components requiring an aesthetically pleasing external appearance.
However, in many applications, ABS resins should also have resistance against strong chemicals such as acetic acid and industrial oils without cracking while maintaining excellent impact resistance, for example, when used in interior and exterior materials of electric and electronic appliances such as mixers, washing machines, electric fans, and the like. Such materials are subject to repetitive stress due to the driving force of motors. Accordingly, such interior and exterior materials should be able to withstand repetitive stress for a predetermined length of time or longer without cracking or breaking.
Recently, there are increasing demands for plastic resins having a variety of special complex properties for use in electronic parts. In particular, electric parts are becoming thinner and more luxurious, thereby increasing the importance of plastic resin properties such as high impact strength, flow property and coloring. Accordingly, the demand for ABS resin having excellent impact resistance and flowability are increasing.
To improve the impact resistance of an ABS resin, the molecular weight of the SAN resin or the rubber content of the ABS resin can be increased. While this may improve impact resistance, however, these techniques fail to improve flowability and heat resistance.